1. Technical Field
The present invention relates to optical scanners and image forming apparatuses.
2. Related Art
For example, as an optical scanner for performing drawing by optical scanning in a laser printer or the like, an optical scanner formed of a torsion oscillator has been known (see, for example, JP-A-2005-181395 (Patent Document 1)).
Patent Document 1 discloses an optical scanner (a light polarizing device) having a frame-shaped supporting substrate, a scan mirror provided inside the supporting substrate, a pair of torsion bars provided coaxially and connecting the supporting substrate and the scan mirror, a permanent magnet provided in the scan mirror, and a coil generating a magnetic field acting on the permanent magnet. The optical scanner of Patent Document 1 is so configured as to turn the scan mirror about a central axis while torsionally deforming the pair of torsion bars by applying an alternating voltage to the coil and thereby alternately changing poles of the magnetic field acting on the permanent magnet.
However, although the optical scanner of Patent Document 1 can turn the scan mirror about the central axis, it cannot displace (move) the central axis. Specifically, the optical scanner of Patent Document 1 cannot move the central axis of the scan mirror arbitrarily in a direction of the thickness of the scan mirror (in a non-driven state) because of the structure of the optical scanner. Moreover, for example, in a state in which the scan mirror is not turned, the optical scanner of Patent Document 1 also cannot displace the scan mirror in the thickness direction thereof while keeping the position thereof. That is, the optical scanner of Patent Document 1 has only one scan mirror driving pattern of turning the scan mirror about a turn central axis fixed to one point. This makes the optical scanner less convenient.